Re: Replacing Parts of a List
- To: mathgroup at smc.vnet.net
- Subject: [mg28760] Re: Replacing Parts of a List
- From: Ignacio Rodriguez <ignacio at sgirmn.pluri.ucm.es>
- Date: Fri, 11 May 2001 20:00:38 -0400 (EDT)
- Organization: UCM
- References: <9dg63q$j5c@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
I guess you want to do the following:
you have Subscript[x,y] and want to set x=10
What you said seems OK for me:
Subscript[x,y]=ReplacePart[Subscript[x,y],10,1]
If you want something simpler, try x=10
If you prefer to have x as a function of Subscript[x,y], then you can use
Evaluate[Subscript[x,y][[1]]]=10
you may see that lhs is x. As Set has Attribute HoldFirst, lhs is not
evaluated unless you explicitly do so.
Roger Jones wrote:
> Given x={1,2} then setting part 1 to 10 (say) is done via x[[1]]=10.
> This
> appealing as it is a condensed notation and is I believe, very
> efficient for large
> arrays.
>
> However, with a subscripted symbol (such as Subscript[x,y]) how is it
> done?
>
> It can be achieved with Subscript[x,y]=ReplacePart[Subscript[x,y],10,1]
> but this is a little unwieldy.
>
> Is there some method (using Hold[Subscript[x,y]] or something like this)
>
> that allows a direct replacement?
>
> Thank you!
>
> -Roger Jones
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Ignacio Rodriguez Ramirez de Arellano
Unidad de RMN
Universidad Complutense
Paseo Juan XXIII, 1
Madrid 28040, Spain
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e-mail: ignacio at sgirmn.pluri.ucm.es
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